c# - Creating treeview from database (Oracle) - WinForms

Question

I have a table with two columns and I want to display them hierarchically in a tree view with a Oracle database binding using Windows Forms (.NET 4.0)

ORGID, PARENTID
======================
1        -         
2        1         
3        1         
4        3         
.....

Being ORGID the parent, and the PARENTID the child (which can also be a parent).

I've tried this:

public partial class OrgHierarchy : Form
{
    DataSet ds = new DataSet();
    TreeNode parentNode = null;

    DataSet RunQuery(String Query)
    {
        DataSet ds = new DataSet();
        OracleConnection con = new OracleConnection(OrgScheme.GetConnectionString());
        DataTable dt = new DataTable();
        OracleCommand cmd = new OracleCommand();
        cmd.CommandText = Query;
        cmd.CommandType = CommandType.Text;
        cmd.Connection = con;
        con.Open();

        OracleDataAdapter da = new OracleDataAdapter(cmd);
        ds = new DataSet();
        da.Fill(ds);

        return ds;

    }

    void CreateNode(TreeNode node)
    {
        DataSet ds = RunQuery("select orgid ,parentid ... 0 and parentid=" + node.Value +" order by parentid,orgid");
        if (ds.Tables[0].Rows.Count == 0)
        {
            return;
        }
        for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
        {
            TreeNode tnode = new TreeNode(ds.Tables[0].Rows[i][1].ToString(), ds.Tables[0].Rows[i][0].ToString());
            tnode.SelectAction = TreeNodeSelectAction.Expand;
            node.ChildNodes.Add(tnode);
            CreateNode(tnode);
        }

    }

    public OrgHierarchy()
    {
        InitializeComponent();

        DataSet ds = RunQuery("select orgid ,parentid .... and parentid is null");
        for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
        {
            TreeNode root = new TreeNode(ds.Tables[0].Rows[i][1].ToString(), ds.Tables[0].Rows[i][0].ToString());
            root.SelectAction = TreeNodeSelectAction.Expand;
            CreateNode(root);
            OrgTree.Nodes.Add(root);
        }

    }
}

I have a number of errors:

Error 1 'System.Windows.Forms.TreeNode' does not contain a definition for 'Value' and no extension method 'Value' accepting a first argument of type 'System.Windows.Forms.TreeNode' could be found (are you missing....

Error 2 The best overloaded method match for 'System.Windows.Forms.TreeNode.TreeNode(string, System.Windows.Forms.TreeNode[])' has some invalid arguments

Help please? I think I'm using Web controls (.Value) which I can't do using WinForms.

you have null in root level in parentID?

Faraz Ahmed
– Faraz Ahmed

2016-09-02 12:35:18 +00:00
Commented Sep 2, 2016 at 12:35 — Faraz Ahmed
– Faraz Ahmed, Commented Sep 2, 2016 at 12:35
@user6002727 exactly

Tiago
– Tiago

2016-09-02 12:41:35 +00:00
Commented Sep 2, 2016 at 12:41 — Tiago
– Tiago, Commented Sep 2, 2016 at 12:41

Faraz Ahmed · Accepted Answer · 2016-09-02 13:46:34Z

First I have Change some logic of your Code

 DataSet ds = new DataSet();
 TreeNode parentNode = null;
 TreeView treeview = null;
 public OrgHierarchy()
 {
    InitializeComponent();

    DataSet ds = RunQuery("select orgid ,parentid .... and parentid is null");
    DataTable dt = ds.Tables[0];
    settingRootLevel(dt);
    if (treeview.Nodes.Count > 0)
    {
            for (int i = 0; i < treeview.Nodes.Count; i++)
            {
                TreeNode node = treeview.Nodes[i];
                addChildNodes(dt, node);
            }
    }

        this.Controls.Add(treeview);

 }

DataSet RunQuery(String Query)
{
    DataSet ds = new DataSet();
    OracleConnection con = new OracleConnection(OrgScheme.GetConnectionString());
    DataTable dt = new DataTable();
    OracleCommand cmd = new OracleCommand();
    cmd.CommandText = Query;
    cmd.CommandType = CommandType.Text;
    cmd.Connection = con;
    con.Open();

    OracleDataAdapter da = new OracleDataAdapter(cmd);
    ds = new DataSet();
    da.Fill(ds);

    return ds;

}

    public void addChildNodes(DataTable dt,TreeNode Node)
    {

        DataRow[] datarows = dt.Select("PARENTID = " + Node.Text);
        for (int i = 0; i < datarows.Length; i++)
        {
                TreeNode node = new TreeNode(datarows[i][0].ToString());
                Node.Nodes.Add(node);
                addChildNodes(dt, node);    
        }
    }

    public void settingRootLevel(DataTable dt)
    {
        DataRow[] datarows = dt.Select("PARENTID is null");

        foreach (DataRow dr in datarows)
        {
            treeview.Nodes.Add(dr[0].ToString());
        }

    }

where settingRootLevel sets all Parent Nodes and addChildNodes run all child with recursion, one more thing is to clearify, kindly make this code in try catch if any exception occured.

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